Box or container of metal sheet having a small thickness and being subjected to high internal pressures

ABSTRACT

This invention relates to boxes or containers of metal sheet having a small thickness and being provided for storage and distribution of beers and other drinks rich in carbonic gas under pressure, with ends made of rolled sheet having a high yield strength of soft steel recrystallized by annealing and the composition of which contains Nb in the range of 0.015 percent to 0.050 percent by weight of the composition.

United States Patent Inventor Jean B. Morjan Koekelberg-Brussels,Belgium Appl. No. 755,209 Filed Aug. 26, 1968 Patented Feb. 9, 1971Assignee Etablissements J. B. Gabriels S.P.R.L.

Koekelberg-Brussels, Belgium a company of Belgium Priority June 14, 1968Belgium 48,034

BOX OR CONTAINER OF METAL SHEET HAVING A SMALL THICKNESS AND BEINGSUBJECTED. TO HIGH INTERNAL PRESSURES 5 Claims, 2 Drawing Figs.

US. Cl 220/67, 148/34 Int. Cl B65d 7/42 Field of Search 148/34, 31,

Primary ExaminerWinston A. Douglas Assistant ExaminerA. SkaparsAttorneyRichards and Geier ABSTRACT: This invention relates to boxes orcontainers of metal sheet having a small thickness and being providedfor storage and distribution of beers and other drinks rich in carbonicgas under pressure, with ends made of rolled sheet having a high yieldstrength of soft steel recrystallized by annealing and the compositionof which contains Nb in the range of 0.015 percent to 0.050 percent byweight of the composition.

PATENTEU FEB I N VE N TOR.

BY Jean 3'. Mega n i k bg guax ATTORNEELS BOX R CONTAINER 0F METAL SHEETHAVING A SMALL THICKNESS AND BEING SUBJECTED TO HIGH INTERNAL PRESSURESThis invention relates to boxes or containers of metal sheet having asmall thickness and being constructed for storage and distribution ofbeers and other drinks rich in carbonic gas under pressure.

The distribution under pressure requires the use of containers having acapacity substantially larger than the conventional storage box. Forinstance, a container has a height of approximately 225 mm. and adiameter of approximately I55 mm., namely a capacity of approximately 4liters. Under an equal pressure, the stress exerted upon the walls ofthe container is thus much more important than in the conventionalstorage box the capacity of which does not generally exceed 1 liter.

The initial pressure being already relatively high, it follows that anyincrease of the room temperature causes a substantial increase of theinternal pressure. This problem is still more important in that themetallic containers or boxes according to the present invention must becapable of withstanding internal pressures resulting, e.g., from thepasteurization temperature, namely about 60 to 65 C. In addition, suchtemperatures may be generally reached incidentally, namely when thecontainers are housed in relatively overheated rooms or locations.

Temperatures between 50 and 60 C. have been observed in the motor cartrunks, as well as in rooms the windows of which are facing south, thepanes forming true lenses concentrating the sun rays upon the metallicboxes and the like.

Generally, by the conventional technical means and compositions and foracceptable thicknesses of approximately 0.32 mm. for the body of thecontainer and 0.60 mm. for the ends, a satisfactory resistance may beonly obtained for internal pressures which do not exceed 4 kg/cm Ofcourse, the use of heavier sheets could be suggested as a solution.Unfortunately, such solution would be unacceptable for both economicaland technical reasons. In fact, it is apparent that owing to theindustrial production means, the raw material has a substantialinfluence upon the cost price of such metallic boxes or containers. Inaddition, it must be also taken into consideration that, owing to theproduction rate, the tools and the good preservation of the industrialequipment, some sheet thicknesses must not be exceeded.

From the above considerations, it results that neither the steelcompositions nor the production means known heretofore allow tomanufacture, within the minimum thicknesses generally used, a metallicbox or container having a sufficient resistance for the storage and thedistribution of beer under pressure with all the safety conditionsrequired by the brewery and without requiring the storage in arefrigerator.

While the manufacture of the body of such cylindrical boxes in tinnedsheet with a thickness of approximately 0.32 mm. does not set anyproblem, the resistance being sufficient, the same is not true for theends, owing to their proper morpholo gy constituting the weak points ofthe container, since it is well known that any excess of internalpressure causes the bulging thereof, with, consequently, a deteriorationof the crimping and other known consequences such as leakages,alteration of the content and the like.

On the other hand, it is not possible to substantially increase thethicknesses of the ends owing to the requirements of the manufactureitself and also for economic reasons. It results that, in the presentstate of the industry, it is not possible to find, in the conventionalgrades generally used in the industry for the manufacture of metallicstorage containers, sheets suitable for the rational manufacture of endsfor containers which must withstand the previously mentioned pressures.

Nevertheless, the object of the present invention is to allow theindustrial manufacture, with the normal tools and equipments, of suchmetallic boxes having a capacity of approximately 4 litres underperfectly acceptable economic conditions, the cost prices being verynear the prices resulting from the use of the conventional sheetsalthough the containers have a substantially increased resistance.

Two metallic containers embodying the present invention are hereinafterdescribed with reference to the appended drawings, wherein;

FIG. I is an exploded view, in cross section of the three parts of thecontainer;

FIG. 2 is partly an elevational view of and partly a section through thecontainer of FIG. I, after assembly.

In these FIGS., 1 shows the body of the container, in this in stancecylindrical; 2 and 3 designate the ends with which the present inventionis particularly concerned.

According to the invention, this resistance increase is obtained, not bythe increase of the thickness of the sheets used for the manufacture ofthe ends, but manufacture a su hstantial increase of the yield strengthof such sheets.

This seems to be simple, but sets truly problems which have appeared tobe very difficult to solve, on one hand because it is not known tomanufacture tinned sheets which. after rolling and annealing, have botha high yield strength of about 40 Kg./mm. and sufficient crimpingpossibilities to allow the manufacture of boxes with the known tools andtechniques and, on the other hand, because the addition of hardeningelements to steel in the proportions necessary for obtaining such highyield strength is not compatible with the requirements relating to thestorage of foods and more particularly to beer.

In fact, it is known that the corrosion of a can by the foods containedtherein depends not only upon the quality and the thickness of the tinlayer, but also upon the composition and the nature of the supportingsheet.

According to the practice defined by national and internationalstandards, the sheet for storage is essentially a sheet made from aneffervescent soft steel in the composition of which are prohibited or atleast limited the hardening ele ments promoting the corrosion such asSi, C, Mn. P, N- Al and Cu are admitted, but they do not allow to reach,in the finished products, a high yield strength together with asufficient elongation. There are also sheets in which a high yieldstrength is obtained by postrolling after annealing, but to theprejudice of the elongation which becomes quite insufficient. (See,e.g., the sheet described in the Gennan Pat. No. 1,247,362 which, for ayield strength of 44.4 kg/mmF, has only an elongation of IO percent upona sample of 5.08 cm.

According of the principal object of the invention, for realizing endsfor the industrial manufacturer of metallic boxes or containers beingpressurized and more particularly of such metallic cylindrical boxes orcontainers having crimped ends and a capacity of approximately 3 to 4litres for containing a liquid under pressure, generally beer, there isused a cold rolled sheet recrystallized by annealing in the top hatfurnace and having a minimum yield strength of 40 kg. and a minimumelongation of 20 percent, said sheet being manufactured from a killedsteel containing, in addition to moderate proportions of ordinaryhardening elements such as C, Si and Mn, a sufficient amount of Nb toreach the said level of yield strength in the cold rolled and annealedproduct, the use of said sheet being combined with the use of aprotecting varnish.

It is apparent that, for solving the specific problems set forth, theinvention used simultaneously three means, namely:

reducing the extent of hardening additions detrimental for corrosion;

increasing, by substantial addition of Nb, the yield strength after coldrolling and annealing, while maintaining sufficient crimpingpossibilities; and

completing the corrosion resistance by the use of a layer of protectingvarnish.

According to the invention, the steel composition meets the followinganalysis:

P 0.040 percent maximum Mn 0.650 to 0.950 percent C 0.060 to 0.100percent Si 0.200 to 0.400 percent Al 0.020 percent minimum Nb about0.020 percent, between 0.010 and 0.030 percent maximum.

Those skilled in the art will very readily conform to the level of theyield strength and the elongation by varying these elements within thespecified limits.

On the basis of the principle of equivalents, the invention claims alsothe replacement of Nb by elements which, like the latter, are likely toinduce a structural hardening by the formation of carbides, nitrides ornitrocarbides, Nb has been specifically selected since it is thecheapest element being used very readily.

It has been established that cylindrical metallic boxes being 225 mm. inheight and 155 mm. in diameter; i.e. boxes having a capacity ofapproximately 4.25 litres, the body being made of a tinned sheet havinga thickness of 0.32 mm. and the ends being made of a steel sheet of thepreviously mentioned composition and being 0.60 mm. in thickness, havehad very good resistance to an extraordinary internal pressure ofapproximately 6 kg./cm. without any detrimental deformation, the saidmetallic boxes being subjected to a temperature of approximately 60" C.The experimented containers contained beer under a C pressure. When thecontainer and content thereof have been brought back to roomtemperature, it has been possible to distribute beer under pressure inabsolutely normal conditions up to the complete emptying. Suchexperiments repeated several hundred of times have all confirmed suchresults.

In this nonlimitative example, the analysis of the sheet was as follows:

P 0.028 percent Mn 0.85 percent S 0.030 percent C 0.082 percent Si 0.320percent A1 0.059 percent Nb 0.026 percent The tinned sheet had thefollowing characteristics:

Yield strength: 41.7 kg./mm.

Break load: 53.2 kg./mm.

Elongation: 24.4 percent R30 hardness: 69

Ericksen: 8.4

It is apparent that the elongation and the Ericksen's value aresubstantially higher than of known tinned sheets having the same yieldstrength (namely the Temper 6 of the American Classification I claim:

1. A metallic box or container made of a sheet having a small thicknessand being subjected to high internal pressures, characterized in havingtwo ends made from a cold rolled soft steel sheet having a yieldstrength higher than 35 kgjmm. and an elongation higher than 20 percent,recrystallized by annealing and the composition of which contains, inaddition to the usual hardening elements an amount of Nb in the range of0.015 percent to 0.050 percent by weight of the composition.

2. A metallic box or container according to claim I, characterized inthat the recrystallization annealing after cold rolling of the sheetused for making both ends is effected in a top hat furnace.

3. A metallic box or container according to claim I, charac terized inthat the steel used for making both ends consists of a carbon steelwhich is manufactured according to the conven tional methods of hotrolling, cold rolling, annealing and skinpass, the recrystallizationannealing after cold rolling being effected in a top hat furnace.

4. A metallic box or container according to claim 1. characterized inthat both ends are made from a cold rolled sheet having a compositionwithin the following limits, by weight of the composition whichadditionally includes:

P 0.040 percent maximum Mn 0.500 to 1.500 percent C 0.050 to 0.200percent S 0.030 percent Si 0.250 to 0.400 ercent Al 0.040 to 0.1 percentCu 0 to 0.400 percent.

2. A metallic box or container according to claim 1, characterized inthat the recrystallization annealing after cold rolling of the sheetused for making both ends is effected in a top hat furnace.
 3. Ametallic box or container according to claim 1, characterized in thatthe steel used for making both ends consists of a carbon steel which ismanufactured according to the conventional methods of hot rolling, coldrolling, annealing and skin-pass, the recrystallization annealing aftercold rolling being effected in a top hat furnace.
 4. A metallic box orcontainer according to claim 1, characterized in that both ends are madefrom a cold rolled sheet having a composition within the followinglimits, by weight of the composition which additionally includes: P0.040 percent maximum Mn 0.500 to 1.500 percent C 0.050 to 0.200 percentS 0.030 percent Si 0.250 to 0.400 percent A1 0.040 to 0.100 percent Cu 0to 0.400 percent.
 5. A metallic box or container according to claim 1,characterized in that the internal walls are covered with a protectinglayer of varnish.